A sensor of this type is known from practice and is used, for example, for determining the soot concentration of an exhaust gas of a diesel engine. This sensor forms a resistive particulate sensor in which at least two electrodes are positioned on a substrate which is manufactured from aluminum oxide or yttrium-stabilized zirconium dioxide having an insulation layer, for example. The electrodes may be implemented as interdigital comb electrodes. Soot particles which accumulate in the area between electrodes short-circuit the electrodes, through which a decreasing electrical resistance between the electrodes is measurable as the particle and/or soot concentration on the sensor surface increases.
Since the electrodes are subjected directly to the exhaust gas flow, in this known sensor corrosion of the electrodes and contamination of the sensor surface with materials may disadvantageously occur, which may have an interfering effect on the measurement.
In diesel engines in particular, the exhaust gas released into the environment is to have the lowest possible soot particle concentration. To monitor the operating status of the internal combustion engine, it is expedient for this purpose to position a soot sensor in the exhaust system associated with the internal combustion engine in order to thus monitor the operating status of the internal combustion engine. The soot sensor may be positioned upstream or downstream from a soot filter. If it is positioned downstream from the soot filter, function monitoring of the soot filter may also be performed using the soot sensor.
A soot sensor of the type described above is susceptible to breakdown under the conditions existing in the exhaust system, however.